1.为什么利率升高的时候会偏好执行put option，利率降低的时候会偏好执行prepayment option?这里面的逻辑是什么？

2.有一段话不理解：Prohibition of all propriatary trading while a firm is in possession of material nonpublic information may be inappropriate, because it may send a signal to the market. In these cases, firms should take the contra side of only unsolicited customer trades. 谢谢老师解释一下！